Let’s say we want to let our users upload images and we want to save them to our .../public/gallery folder using Paperclip. But we want to add them dynamically, based on another field of our model.

For example, if we have a User model with the field category (nature, vehicles, etc.) and gallery_img being the actual file we upload.

We want to store files like this:

.../public/gallery/nature/forest.jpg

.../public/gallery/vehicles/jaguar.jpg

.../public/gallery/vehicles/bike.jpg

where nature or vehicles is the current_user.category field.

This is how we do it:

class User < ActiveRecord::Base

    has_attached_file :gallery_img,
       :url => "/gallery/#{self.to_s.downcase.pluralize}/:filename",   
       :path => ":rails_root/public/gallery/#self.to_s.downcase.pluralize}/:filename"

    validates_attachment :gallery_img,
        :content_type => { :content_type => ["image/jpeg", "image/gif", "image/png"] }

end

#{self.to_s.downcase.pluralize} will set the current model lowercased and pluralised. In our case User will become users

:url will set the url for reading the file. put it in view as: current_user.gallery_img.url

:path is the path where the file will be stored by Paperclip

Ensure :url and :path point to the same file!

And now:

When we have a user uploading a file e.g. forest.jpg, the file will be saved in .../public/gallery/nature/forest.jpg and can be accessed at localhost:3000/gallery/nature/forest.jpg

Notice:

Default path can be set in the evnironment files in case the models has_attached_file does not specify the path and url.

in /config/environments/development.rb:

  Paperclip::Attachment.default_options.merge!({

    :url => "/gallery/other/:filename",

    :path => ":rails_root/public/gallery/other/:filename"

  })

Paperclip stores files by default in: /system/:attachment/:id/:style/:filename

(all symbols from the path are dynamic fields)

To also add current environment to the path use:

 :url => "/#{Rails.env}/gallery/other/:filename",

 :path => ":rails_root/public/#{Rails.env}/gallery/other/:filename"

Tip:

put the has_attached_file and it’s validations in a separate model concern module.

I hope this helped.

Happy coding.